Cascade reactors for long-life solid-state sodium-air batteries.

Sun, Xue; Li, Haitao; Song, Yajie; Liu, Jiaxuan; Ji, Pengxiang; Lei, Xincheng; Zhang, Xiangzhi; Liu, Qingsong et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Sodium (Na)-air batteries show significant potential as alternatives to lithium-air batteries due to their high theoretical energy density and the abundant availability of sodium reserves. Nevertheless, the formation of complex products, specifically NaO<sub>2</sub>, Na<sub>2</sub>O<sub>2</sub>, Na<sub>2</sub>CO<sub>3</sub>·xH<sub>2</sub>O, during the multi-step reactions inevitably raises reconciled potential incompatibility that causes low efficiency and large overpotential. Here, we introduce a cascade electrocatalysis strategy that involves switchable metal and oxygen redox chemistry through electrochemical potential tuning. Leveraging the lithium ion spatial pinning effect, sodium ions trigger in the Na[Li<sub>1/3</sub>Ru<sub>2/3</sub>]O<sub>2</sub> electrode system to toggle the geometric state at a low electrochemical potential and oscillate among different catalytic states to achieve sequential conversion of complicated multi-step intermediates. The Na[Li<sub>1/3</sub>Ru<sub>2/3</sub>]O<sub>2</sub> catalyst effectively compartmentalizes the threshold potential that circumvents deactivating or competing pathways while coupling different catalytic cycles. As a result, the sodium-air battery employing this catalyst exhibits long-term reversibility over 1000 cycles with a decent catalysis efficiency exceeding 99%. Our results demonstrate that the cascade electrocatalysis strategy contributes to the design of integrated sodium-air batteries with long-term cycling stability.